JPH0523982B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to fluid assistance devices, and more particularly to fluid assistance devices for brake circuits that combine hydrodynamic and hydrostatic actuation (commonly known as the term "full power"). It is.

A fluid assistance device of the type known as "Full Power" is disclosed in French patent application no.
03105, the device is adapted to operate hydrostatically as a conventional master cylinder in the event of a failure of the high-pressure circuit. The above device is the first
An annular cup is provided separating the pressure chamber from a second pressure chamber, the second pressure chamber being connected to the brakes of the vehicle and adapted to be connected to a source of high pressure fluid. In the event of a failure in the high-pressure circuit, when the assist device is activated, a piston defining a first pressure chamber moves to compress the fluid in this chamber, and the cup can be tilted to allow pressure fluid to flow to the brake. .

Although the above device has clear advantages, it suffers from the disadvantage that it requires a large number of passages through the piston and other associated components.

It is therefore an object of the present invention to develop a hydraulic fluid of the type known as "full power", which can act as an ordinary master cylinder in the event of a failure in a high-pressure circuit, and which is simple in construction, highly reliable, and inexpensive to manufacture. The goal is to provide assistive devices.

To achieve this objective, the present invention comprises a casing provided with a hole, a casing slidably fitted within the hole, and a casing provided with a hole.
a first piston movable between a first position in which a first chamber connected to a brake of the vehicle is isolated from a source of high-pressure fluid by action of a brake pedal and a second position in which the first chamber is in communication with a source of high-pressure fluid; , a second chamber formed in the casing, a first passage connecting the first and second chambers, and a first passage disposed within the first passage.
The first normally closes the passage under the action of the pressure in the room.
A fluid assistance device comprising a valve device and means for isolating between the first chamber and the high pressure fluid source in the event of a failure of the high pressure fluid source, the second passage communicating the second chamber with the low pressure reservoir; a second valve arrangement disposed within the first and second chambers, the second valve arrangement being responsive to pressure within the first and second chambers to normally isolate the second passageway from the second chamber during brake application; The present invention proposes a fluid assistance device characterized in that fluid is sometimes caused to flow from a second chamber to a reservoir.

These and other features and advantages of the invention will become apparent from the following description of an embodiment, made with reference to the accompanying drawings.

As shown in the drawing, the fluid aid device is
A casing 10 is provided with a low-pressure fluid reservoir 12 mounted thereon. The casing 10 includes a bore 14 in which a piston 16, driven by a brake pedal (not shown), is slidably fitted. A retaining member forming housing 18 is mounted within bore 14 and includes a push rod 20 with a coil spring 22 disposed around the push rod. A sleeve 24 is fixedly fitted within the bore 14 of the casing 10 and defines a first pressure chamber 26 with the piston 16 . A control piston 30 is slidably fitted within the central bore of the sleeve 24 with a slight clearance and includes an axial passage 32 connected to an orifice 33. The passage 32 is provided with a valve seat 34 of an inner diameter equal to the diameter of the control piston 30. Valve seat 34
cooperates with a ball valve 36 which is held within the housing 18 with a small clearance. control piston 3
0 also includes a push rod 38 which, during the movement of the control piston 30 to the left in the figure, can abut the ball valve 40 and lift this valve from the valve seat 42, the ball valve 40 being normally supported by a spring 4.
1 against the valve seat 42. Opening of ball valve 40 allows fluid from high pressure fluid source 44 to flow into second pressure chamber 46 defined between sleeve 24 and plug 48 . The pressure chamber 46 is
at least one groove 49 and orifice 5 formed in the end of the sleeve 24 opposite the plug 48;
0 to the brake 52 of the vehicle.

The sleeve 24 also includes first and second pressure chambers 26,
Stepped hole 54 and hole 5 forming a passage connecting 46
5, this passage is normally closed by a ball valve 56 pushed towards the valve seat 58 by a weak spring 61. The sleeve 24 further includes:
A third passageway or stepped hole 60 is connected to the annular space by an aperture 62 in the wall of the sleeve, which is in fluid communication with the low pressure reservoir 12 via an aperture 64 . A ball valve 66 is mounted within the bore 60 and abuts a small diameter needle 68 which slides within a cooperating bore 70 with a small clearance. A spring 72 is mounted so as to be freely movable within the bore 60, abuts the ball valve 66, and normally projects into the first pressure chamber 26. The diameter S1 of the area of the bore 60 forming the valve seat 74 for the ball valve 66 is considerably larger than the diameter S2 of the needle 68.

When the fluid assist system is activated, during normal operation piston 16 moves to the left, displacing housing 18 via spring 22. Housing 1
8 closes the ball valve 36 and opens the ball valve 40 via the control piston 30,
Via the second pressure chamber 46, the groove 49 and the orifice 50, pressure fluid can flow to the brake 52 of the vehicle. During braking, the pressure in the second pressure chamber 46, which is several times greater than the pressure in the first pressure chamber 26, acts on the needle 68 to keep the ball valve 66 in the closed position. The ball valve 56 remains closed due to the action of high pressure fluid flowing from the second pressure chamber 46 to the hole 54 . Pressure fluid also acts on the housing 18 via the control piston 30 and the ball valve 36;
It thus generates a force that is commensurate with the control force applied by the brake pedal. In this way, the perfectly regulated brake pressure corresponds to the control pressure.

When the piston 16 of the master cylinder moves to the left in the figure, the pressure π in the chamber 26 is equal to the brake pressure x
The pressure in chamber 26 is returned to reservoir 12 via ball valve 66 to be equal to S2/S1. This pressure π acts on the cross-sectional area of the piston 16 and acts as a pedal sensing pressure.

When the brake pedal is released, the piston 16
moves back to the right due to the action of multiple preloads. Brake pressure is provided by orifice 50, groove 49, and second pressure chamber 4.
6, through the passage 32 of the control piston 30, the open ball valve 36, and the gap between the bore 14 and the housing 18 to the first pressure chamber 26, and excess fluid flows through the open ball valve 66; It is discharged through hole 60 and opening 62 into low pressure reservoir 12 . If the brake release is interrupted at a certain position, the ball valve 36 closes again and the brake pressure stabilizes at the corresponding value.

In the event of a failure in the high-pressure circuit, for example if the pump or accumulator stops working, the ball valve 4
A valve (not shown) upstream of 0 closes to isolate the fluid assistance device from the high pressure circuit. When the brake is applied, the housing 18 is moved by the spring 72.
the spring 72 holds the ball valve 66 on its seat 65, closing the hole 60 and opening the first pressure chamber 26 to the reservoir 1.
Block from 2. The movement of the piston 16 causes the first
While the pressure in pressure chamber 26 increases, ball valve 66 remains in the closed position. The pressure fluid in the chamber 26 opens the ball valve 56, causing the holes 54, 55, the second pressure chamber 46,
Brake 52 via groove 49 and orifice 50
distributed in The fluid assist device will therefore operate as a normal master cylinder. The ball valve 36 becomes inoperative as soon as the housing 18 contacts the sleeve 24 when the brake is released.
is in a substantially free state, so the brake pressure passes through the orifice 50, the groove 49, the second pressure chamber 46, the passage 32 and the ball valve 36, and then the brake pressure is transferred to the first pressure chamber 26.
and is discharged to reservoir 12 via ball valve 66, hole 60 and opening 62.

The fluid assist device described above is for use in a single brake circuit. In practice, a system with two identical aids combined with corresponding brake circuits would be used. In this latter case, it is advantageous for the two assistance devices to be arranged in the same casing.

[Brief explanation of the drawing]

The drawing is a partial longitudinal sectional view of a fluid assistance device according to the invention. 10...Casing, 12...Low pressure reservoir,
14, 70... hole, 16... piston, 24...
Sleeve, 26, 46... Pressure chamber, 44... High pressure fluid source, 52... Brake, 54, 60... Stepped hole, 56, 66... Ball valve, 62... Opening, 6
8... Needle.

Claims (1)

[Scope of Claims] 1. A casing 10 provided with a hole 14 and a first chamber 46 slidably fitted in the hole and connected to a brake 52 of a vehicle by the action of a brake pedal from a high-pressure fluid source 44. a first position for blocking and a first chamber 4;
a first piston 16 that is movable between a first piston 16 and a second position that communicates the casing 1 with the casing 1 and a second position that communicates the casing
0, a first passage 54 connecting the first and second chambers 46, 26; a first valve arrangement 56 for normally closing the passageway 54;
a second passageway 60 communicating the second chamber 26 with the low pressure reservoir 12; a second valve device 66 disposed within the second passage 60;
6 is responsive to the pressure within the first and second chambers 46, 26 to normally isolate the second passageway 60 from the second chamber 26 during brake application, while directing fluid from the second chamber 26 to the reservoir 12 upon brake release. A fluid assisting device characterized in that it allows fluid to flow. 2. Claim 1, characterized in that the second valve device 66 has an area exposed to the first chamber 46 that is smaller than an area exposed to the second chamber 26.
Fluid aids as described in Section. 3. Fluid assistance device according to claim 2, characterized in that the second valve device consists of a ball valve 66 with a drive device 68 projecting into the first chamber 46 through a hole 70. 4. The fluid assistance device according to any one of claims 1 to 3, wherein the first valve device comprises a ball valve 56. 5 Sleeve 24 with two holes 54, 60 separating first chamber 46 from second chamber 26 and associated with first and second valve devices 56, 66, respectively.
A fluid assistance device according to any one of claims 1 to 4, characterized in that a fluid support device is disposed within the hole 14.